1,2,4-Triazol-5-one (or its tautomeric form; 5-hydroxy-1H-1,2,4-triazole) is a known compound, commonly referred to as "TO" and useful as an intermediate in the production of explosives which are relatively insensitive to shock, impact, and friction, and in the synthesis of dyestuffs. In practice, the TO intermediate is nitrated to produce 3-nitro-1,2,4-triazol-5-one which is used in explosive compositions. The presence of chloride ion concentrations in TO is undesirable since the presence of chloride ion stored in explosives results in increased corrosion of the casings and unwanted gas formation.
Unfortunately, prior art processes for the production of TO have generally utilized semicarbazide hydrochloride as a reactant resulting in the presence of the unwanted chloride ion in the TO product. By way of illustration, European Patent Application 0 210 881, published Apr. 2, 1987 in the name of Becuwe, discloses a process for preparing 1,2,4-triazol-5-one in which formic acid is pre-heated to 70.degree.-75.degree. C. and semicarbazide hydrochloride added to form a reaction mixture. The reaction mixture is then heated to produce a product which is subsequently evaporated to dryness. As another illustration, U.S. Pat. No. 4,733,610, issued Mar. 29, 1988 to K-Y Lee et al discloses a process for preparing 1,2,4-triazol-5-one in which a mixture of semicarbazide hydrochloride and formic acid is heated, and then concentrated by distillation of excess formic acid until the desired product crystallizes.
Heretofore, processes for making TO without the use of a chloride-containing reactant have not been known to the knowledge of the present inventor. New processes which do not utilize a chloride-containing reactant and which produce a chloride ion-free TO product would be highly desired by the NTO manufacturing industry.